* .gitignore: add etc/guix-publish.conf and /etc/guix-publish.service.
* etc/guix-publish.conf.in: New file.
* etc/guix-publish.service.in: New file.
* nix/local.mk (etc/guix-%.service, etc/guix-%.conf): Generalized former
build-rules for by using patterns.
(nodist_systemdservice_DATA): Add etc/guix-publish.service, update
comment.
(nodist_upstartjob_DATA): Add etc/guix-publish.conf, update comment.
* doc/guix.texi (Invoking guix publish): Add description for enabling
"guix publish" on host distros using the new files.
* doc/local.mk: Use "%D%" for the directory of the fragment relative to
the base 'Makefile.am'.
* emacs/local.mk: Likewise.
* gnu/local.mk: Likewise.
* nix/local.mk: Likewise.
This follows a convention used by some other GNU packages like Autoconf,
Bison, Coreutils, and Gnulib.
* doc.am: Rename to ...
* doc/local.mk: ... this.
* emacs.am: Rename to ...
* emacs/local.mk: ... this.
* gnu-system.am: Rename to ...
* gnu/local.mk: ... this.
* daemon.am: Rename to ...
* nix/local.mk: ... this.
* Makefile.am: Adapt to them.
* doc/guix.texi (Porting to a New Platform): Adapt documentation.
* guix/config.scm.in (%state-directory, %config-directory): Adapt comments.
* emacs/guix-config.el.in (guix-config-state-directory): Likewise.